Passive Radio-Frequency Repeater for Enhancing Signal Reception and Transmission in a Wireless Charging Platform

This paper reports new results of an emerging field that combines radio-frequency (RF) repeater design and wireless power technologies for charging applications. Power electronics-based wireless charging pads have recently been developed for charging portable electronic devices such as mobile phones. However, the electromagnetic shield underneath the pad could reduce transmission and reception signals. In this paper, a novel passive RF repeater for a wireless charging platform is proposed and investigated for mitigating the signal blocking problem. Since the effective shielding structure for the low-frequency charging signal is not RF friendly, the received RF signal of a wireless mobile device can be reduced when the phone is placed on a wireless charging platform. A dual-polarization free-positioning passive RF signal repeater has been successfully designed and implemented. It can improve the RF reception signal strength by at least 3.6 dB without noticeable reduction in energy efficiency in the charging process.